The bolt on the cables that screw into the battery are just sightly too long. I was having batteries fail that always leaked from the battery connection point. I solved that problem by shortening the bolts slightly so that the bolts would not bottom out in the battery.While we're talking about batteries:
- It's worth noting on side post batteries to NOT crank the bolts in when tightening - you may cause a leak or weaken the connection to the internal plates.
- Did these cars come with a battery blanket when new? These cars do a good job isolating the battery from engine heat but that's not a benefit in the winter.
I have had great luck with the Optima Yellow Top AGM battery. It is a deep cycle battery that can be severely discharged without damaging the battery. I also keep my battery connected to a Marine battery maintainer when I am not driving my Impala. I gave a Guest 2711A ChargePro mounted to the wall next to my Impala in my garage. When I come home from a drive, I pop the hood and connect the charger. My Impala will sometimes sit for 2 months without driving.
I also have the Optima Yellow Top in my GTO for the same reason. Not a daily driver.